WASHINGTON -- Now here's a tag team for the ages: Richard Nixon, Mitt Romney, Barack Obama.

The arc of history joins all three in the cause of universal health care, a goal promoted by Nixon four decades ago and advanced in laws enacted by Romney and Obama in turn. So where are the high fives between the president and the former Massachusetts governor?

The most significant health care law since Medicare gets barely a shout-out from Obama. And when Romney must talk about the law he won in Massachusetts, it's because someone's got him on the defensive in the Republican presidential primary campaign.

"Big health care reform turns out not to be very popular _ and actually unhealthy for the candidates who did it," says Robert Blendon, a Harvard professor who tracks public opinion on the subject.

The Supreme Court will decide if the new federal health care overhaul or any part of it is unconstitutional after arguments next week. If the law that Republican opponents call "Obamacare" survives, "Romneycare" will stand in the history books as a guidepost for it, hardly the first time a state has served as a laboratory for national social policy.

The federal and Massachusetts laws share much, including a requirement that individuals carry health insurance, a provision that taxpayers provide help for those who can't afford it and protections against denial of coverage. And ObamaRomneycare shares more with Nixon's never-implemented approach _ an insurance system anchored in the private market with a hefty government safety net _ than with the Clinton administration initiative that collapsed in the 1990s under the weight of its own complexity and reach.

Obama and Romney are not overly modest men, but you might think so when it comes to this subject.

Health care got two sentences in Obama's State of the Union speech, one more than he devoted to an unfair-trade case against Chinese tires. Romney sticks to the Republican line that Obama's law must be repealed, and gives so-so reviews of his own law. "Some things worked, some things didn't, and some things I'd change," he says when pressed.

Stuart Altman has been in the thick of it all as a health policy economist who advised Nixon in the 1970s and four more presidents of both parties since. He also co-chaired a Massachusetts task force on health policy in the prelude to Romney's initiative.

"Poor Romney, he has to run away from it," Altman said, simply because Republicans have made it their refrain that "Obamacare" must go, and Romney's plan can't easily be divorced from it.

"While Obama's not running away from it, he's not actively selling it, and from my point of view that's unfortunate," said Altman, who supports the law. "It needs a very substantial champion. It needs some substantial selling. Right now the negatives are outweighing the positives, in terms of sales, by about 100 to 1."

In a dozen speeches or remarks in public settings last month, Obama spoke not a word about the law, even as his administration churned out press releases about its benefits. But he does sell the initiative to crowds that have already bought it: It's a standard applause-generator in his remarks to Democratic fundraisers.

The crucial difference between the Romney and Obama plans is the most obvious: One is state, the other is federal. Romney argues that states must be free to draw up their own plans to expand health coverage and the feds have no business imposing a national solution, a point at the center of the Supreme Court case. Moreover, the federal law is designed to be paid for in part by cutting money from Medicare, which creates political opposition that states wouldn't face.

But both penalize people who don't buy insurance and businesses that don't offer it to employees, with exceptions for the smallest companies. They both rely on new health insurance marketplaces, called "exchanges" in the federal law, to give individuals outside the employer-supported insurance system a choice of plans. Both laws subsidize workplace-based insurance and coverage for people making well above the poverty level, not just the poorest.

Romney acknowledged the similarities in a less politically charged time for him, during his 2010 book tour, and praised the individual insurance mandate that, for conservatives, has become the most contentious part of the overhaul. Speaking to the Emory University student newspaper, he said of Obama: "And some of the best features of his health care plan are like ours _ such as, we do not allow insurance companies to drop people who develop illnesses, our insurance is entirely portable, virtually all of our citizens are insured and there is an individual responsibility for getting insurance."

He went on to criticize the "one-size-fits-all solution" from Washington and emphasized his preference for plans devised by each state.

Romney's law is credited with expanding coverage but not controlling costs, which it did not set out explicitly to do. Public opinion surveys in Massachusetts consistently suggest it is well regarded, and there has been no serious effort to roll it back.

"It's almost as if we're discussing poll results from a separate country," Blendon says.

And the state law has an advantage over the federal one in winning public support: the passage of time.

"In Massachusetts, in the sixth year of the program, it would be very hard to envision that we're going to take away insurance coverage from all the people who got coverage and say let's go back to six years ago," Blendon said.

In contrast, people have been slow to see the benefits of Obama's law _ or to experience any downside _ because the bulk of it does not kick in until 2014.

Nixon's initiative was bold for its time _ and even bolder now _ because it contained measures that have become anathema to the Republican mainstream, including a requirement that all employers offer coverage to their workers. To his everlasting regret, Democratic Sen. Ted Kennedy, his party's broker on health care, chose not to seal a deal with Nixon along those lines, reasoning that a Democratic president down the road could achieve a single-payer government system like Canada's.

"You never know how the thing would have played out," said Altman, an architect of Nixon's initiative and author of a new book on the century-long struggle for expanded medical care, "Power, Politics, and Universal Health Care." "There was no question that the stars were aligned in 1974 for the passage of something important."

Nixon declared, "The time is at hand this year to bring comprehensive, high-quality health care within the reach of every American. I shall propose a sweeping new program that will assure comprehensive health insurance protection to millions of Americans who cannot now obtain it or afford it."

With the Watergate scandal soon to destroy Nixon's presidency, health care was surely a topic he preferred to talk about. It's just not one that Romney or Obama want to talk about now.